The present invention relates to a shock absorber loaded in the inner cavity of a tire enclosed by a tire for a two-wheeler and a rim, particularly a shock absorber that gives excellent steering stability both when starting running and during running of a two-wheeler.
Tires of two-wheelers (such as motorcycles, bicycles) that run mainly on paved roads are filled with air on the inside of the tire in the same manner as four-wheelers and the air absorbs the shock from the road. For example, in the case of a tire having a tube, the tube is filled with air and in the case of a tubeless tire, air is filled directly into the inside of the tire.
In contrast, among two-wheelers that are designed to run on unpaved roads (off-roads), tires of those for intense running such as for jumping receive strong shock when landing and run on road surfaces having sharp bumps. Therefore, there is the problem that tires filled with air are punctured if used for such vehicles. In order to solve this problem, JP-A-7-186610 discloses the method of introducing a shock absorber having closed cells in the inner cavity of a tire enclosed by the tire and the rim instead of air to give cushioning property to the entire tire.
However, even when the shock absorber has sufficient cushioning property when starting running, the temperature of the shock absorber increases while repeating compression and recovery in the tire by running and the inner pressure of the cells in the shock absorber increases. In order to counteract this phenomenon, the shock absorber expands and when expansion of the shock absorber is ceased by the inner wall of the tire, the pressure increases. In this way, the elasticity of the shock absorber, which had sufficient cushioning property when starting running, increases and the tire can no longer absorb shock, thus causing steering stability to become poor. Even when the shock absorber is softened in order to prevent increase in elasticity of the shock absorber by running, the cushioning property when starting running becomes poor.
Thus, a shock absorber that exhibits sufficient hardness (storage modulus) both when starting running and during running of a two-wheeler is desired.